VR specific controls
Toggle trade direction
In the barter menu or the gift menu, keep hitting "left" until you've reached the first item on the category list (titled "All"). Hit "left" again and the trade direction should toggle.
Sorting items
This applies to any screen where you can see an inventory list. With the first item in the list selected (or nothing selected), hit "up" once to move the sorted column to the next one. Hit "up" twice in quick succession to change the sort direction.
For trackpad users, try using "slow swipe" and "fast swipe" to differentiate between these two actions. The number of controller vibrations indicates how many "up" events the game has registered.
Requirements
SKSE VR
Skyrim VR Tools
Recommended mods
VR Menu Mouse Fix